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Definition: Chromosomes from Black's Medical Dictionary, 43rd Edition

The rod-shaped bodies to be found in the nucleus of every cell in the body. They contain the GENES, or hereditary elements, which establish the characteristics of an individual. Composed of a long double-coiled filament of DNA, they occur in pairs – one maternal, the other paternal – and human beings possess 46, made up of 23 pairs. The number of chromosomes is specific for each species of animal. Each chromosome can duplicate an exact copy of itself between each cell division. (See GENETIC CODE; GENETICS; HEREDITY; MEIOSIS; SEX CHROMOSOMES.)

chromosome

From The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide
Structures in a cell nucleus that carry the many thousands of genes , in sequence, that determine the characteristics of an organism. There are 46 chromosomes in a normal human cell. Each chromosome normally consists of one very long double strand (or molecule) of DNA , coiled and folded to produce a compact structure. The exception is just before cell division when each chromosome contains two double strands of DNA, a result of the copying of each molecule of DNA. The point on a chromosome where a particular gene occurs is known as its locus. Most higher organisms have two copies of each chromosome, together known as a homologous pair (they are diploid ) but some have only one (they are haploid ). See also mitosis and meiosis . In a working cell chromosomes exist in a less dense form called chromatin and cannot be seen using a laboratory light microscope. However, during cell division they get shorter and fatter and so become visible. When pictures are seen of chromosomes, they have…
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Full text Article chromosome

From Philip's Encyclopedia
The 46 chromosomes in somatic (non-reproductive)...
Structure carrying genetic information, found only in the cell nucleus of eukaryotes . Thread-like and composed of DNA , chromosomes carry a specific set of genes . Each species usually has a characteristic number of chromosomes; these occur in pairs, members of which carry identical genes, so that…
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Full text Article Chromosomes

From Encyclopedia of Insects
Mitotic and meiotic holocentric chromosomes in an...
Chromosomes in insects display almost the whole range of variation seen in the chromosomes of higher plants and animals. In these groups the deoxyribonucleic acid (DNA), which contains the genetic code determining development and inheritance, is contained in a nucleus in each cell. At interphase, …
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Full text Article chromosome

From The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide
Structures in a cell nucleus that carry the many thousands of genes , in sequence, that determine the characteristics of an organism. There are 46 chromosomes in a normal human cell. Each chromosome normally consists of one very long double strand (or molecule) of DNA , coiled and folded to produce…
| 495 words
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Full text Article chromosome

From Britannica Concise Encyclopedia
During the first stages of cell division, the...
Microscopic threadlike part of a cell that carries hereditary information in the form of genes . A defining feature of any chromosome is its compactness, which helps organize genetic material for cell division and enables it to fit within structures such as the cell nucleus or the head of a viral…
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Full text Article Chromosome

From Brenner's Encyclopedia of Genetics
Chromosomes are the physical carriers of genes, consisting of DNA and associated proteins. Bacteria typically have one circular chromosome, while eukaryotes usually have linear chromosomes and vary widely in their sizes and numbers of chromosomes. All chromosomes have the capacity to transmit genes…
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Full text Article chromosome

From The Columbia Encyclopedia
(krō'mӘsōm´´), structural carrier of hereditary characteristics, found in the nucleus of every cell and so named for its readiness to absorb dyes. The term chromosome is usually reserved for the structure when it is condensed and readily visible during cell division (see mitosis ). At other times…
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A chromosome is a long strand of DNA (deoxyribonucleic acid) that has bundled itself together in order to replicate. Within the nucleus of every human cell (except gametes – egg and sperm cells) there are 46 chromosomes, which together contain all an individual’s genetic information. There are two…
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Full text Article chromosome

From Dictionary of Microbiology & Molecular Biology
In a prokaryotic cell, or in the nucleus of a eukaryotic cell: a structure consisting of or containing DNA which carries genetic information essential to the cell; the term is also commonly applied to DNA in a mitochondrion or chloroplast and to the genome of a DNA virus, but generally not to the…
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From Penguin Dictionary of Biology
It is difficult to think of structures with greater biological importance (see GENETIC VARIATION , RECOMBINATION ). Literally, a coloured (i.e. stainable) body; originally observed as threads within eukaryote nuclei during mitosis and meiosis. Composed of nucleic acid, most commonly DNA, usually in…
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Full text Article chromosome

From Collins Dictionary of Medicine
One of the discrete coiled DNA and protein structures, present in all animal and plant cells, which carry the genetic code for the construction of the body of the organism. Chromosomes are DNA bound to the protein histone in an enormously condensed manner. The packing ratio (DNA length divided by…
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